In the past, there has been used an optical coherent tomography apparatus (Optical Coherent Tomography: OCT) for diagnosing arteriosclerosis, for diagnosis before operation at the time of treatment inside a blood vessel depending on a high functional catheter such as a balloon catheter, a stent and the like or for a result confirmation after an operation. In an optical coherent tomography apparatus, radial scan is carried out by inserting a catheter installed with an optical fiber which is attached with an optical lens and an optical mirror at the distal end thereof into a blood vessel, by illuminating light into a blood vessel while rotating the optical mirror and by receiving reflected light from a biological tissue. Then, in the optical coherent tomography apparatus, a cross-sectional image of a blood vessel is drawn-out (prepared) based on the reflected light obtained by this radial scan. Further, as an improvement of the optical coherent tomography apparatus, there has been developed an optical frequency domain imaging apparatus utilizing a wavelength sweep (see, for example, Japanese unexamined patent publication No. 2009-128074).
The optical coherent tomography apparatus, inside the apparatus, divides a light outputted from a light source into a measurement light and a reference light, and emits the measurement light from a distal end thereof through an optical fiber inside a catheter. Then, by taking-in a reflected light reflected from a biological tissue inside the apparatus through the same optical fiber, and by making the reflected light and the reference light interfere each other, it is possible to obtain intensity of the measurement light from the same optical path length as that of the reference light, more specifically, to obtain intensity of the reflected light.
In the optical coherent tomography apparatus as mentioned above, a reflected light is obtained by reflecting the reference light on the mirror inside the apparatus and concurrently, the optical path length of the reference light is scanned by moving the mirror position forward and backward. Then, owing to a fact that a coherent light between the reference light and the reflected light is obtained in synchronization with the scanning of this optical path length, it is possible to obtain reflection-intensity distribution in the depth direction. In an optical coherent tomography apparatus, a radial scan is carried out by rotating the optical fiber axially and a blood vessel cross-sectional image is drawn out.
On the other hand, there has been proposed an optical frequency domain imaging apparatus in which a cross-sectional image is formed by utilizing a wavelength sweep instead of changing the optical path length of the reference light. In an optical frequency domain imaging apparatus using the wavelength sweep, there is obtained a reflection-intensity distribution of the depth direction with reference to a point, at which the optical path difference between the measurement light and the reference light is same, from the frequency distribution of the obtained coherent light by sweeping the wavelength of the emitted light repeatedly without scanning the optical path length of the reference light.
In an ultrasonic diagnosis apparatus, a pull-back operation (operation of axially moving an ultrasonic transducer) is carried out at a speed around 1 mm/sec, so that it was possible for an operator to set an area to be observed while confirming the picture screen. On the other hand, in an optical coherence diagnosis apparatus, data are obtained speedily during the period of removing blood depending on flash liquid, so that usually there is employed a system in which a distance as long as possible is recorded at once and a slow reproduction is carried out later on. At that time, the position for recording the image is confirmed while observing a CAG or OFDI image, but there was no other way than a way in which the record termination is carried out by a manual termination operation or by thoroughly pulling all the distance which can be pulled-back.
Usually, a guiding catheter is used for guiding a probe which contains a catheter sheath and an imaging core until a cross-section imaging position is reached inside a blood vessel. For example, a guiding catheter is passed-through until reaching a vicinity of the imaging position of a coronary artery by way of a femoral artery and the probe is guided to the imaging position by using a guide wire. Therefore, at the time of such a procedure, for example, as shown in FIG. 6, it happens that a scan will be carried out by protruding a probe which includes a catheter sheath (301) and an imaging core (601, 602, 231) from a guiding catheter. For that reason, a transmitting and receiving unit for transmitting a measurement light and receiving a reflected light on the way of pull-back scan enters the inside of the guiding catheter. When the transmitting and receiving unit enters the inside of the guiding catheter, the measurement light to the portion desired to be observed or the reflected light from the portion desired to be observed will be blocked and significant data cannot be obtained even if the recording is continued. However, as a result of analyzing the data obtained at a facility in cooperation with a well trained technical expert, a guiding catheter was recorded for the length of 30% to 60% of the obtained data and these data are thoroughly unnecessary data. The problem caused by recording unnecessary data in this manner will be described hereinafter.
When recording an image, some sort of flash liquid is injected by an injector, a contrast syringe or the like in order to remove blood. For example, when selecting a contrast agent as the flash liquid, usually, it happens that a quantity of around 10 ml to 20 ml is to be injected per one pull-back scan, and several 10% thereof are the quantity which is injected after the probe enters the guiding catheter. There is possibility that the injection of such a flash liquid may exert influence on a renal function or another physiological function of a patient and it is thus preferable to limit the injection of the flash liquid to a requisite minimum value.
In addition, by recording a useless image, the data volume will increase by an amount of around a few 10 percent to a hundred percent, it is needless to say that the time period required for the data handling also increases, and the time period which can be used for the diagnosis under normal circumstances will be compressed. Further, the space necessary for storing inspection data will also increase by a similar ratio.